I have taken a look at the recalibrated C01 frames for LLO and LHO. See LLO alog 21961 , for the LLO version of this. I grabbed the H1:GDS-CALIB_STRAIN (online) and H1:DCS-CALIB_STRAIN_C01 (recalibrated) data from the Caltech cluster, and generated the ratio of the spectrum at time which we expect both the C01 and C00 to be correct. The data is stored in the calibration svn at: https://svn.ligo.caltech.edu/svn/aligocalibration/trunk/Runs/O1/H1/Results/C01 It was generated by the script: https://svn.ligo.caltech.edu/svn/aligocalibration/trunk/Runs/O1/H1/Scripts/CHECKS/compare_C00_C01.m Below I attach a ratio of the strain between C01 and C00, from GPS 1128249017 (Oct 7, 2015 10:30 UTC). This is a time period when the front end models and GDS pipeline matched our best knowledge of the instrument and were used to generate the recalibrated C01 data. This should be compared to LHO alog 22291 , first attachment. Similarly to LLO (see LLO alog 21357 ), we believe the small 2% differences at low frequency are due to minor mismatches in the front end filter realization against our full calibration model which the GDS filters match well against. The large narrow frequency 5% differences are around the DARM calibration line (at 37.3 Hz) is similar to LLO (see 21961 ). The other higher discrepancy is I believe related to the front end filtering handling of certain notches, which Kiwamu had to reduced the Q for in the calibration. See LHO alog 21332 and 22738 .
The issue with the front-end filters around the violin modes (see 22631) was only present in the C00 calibration between 0200 Sep 11 and 1600 Sep 14, so I think this does not appear in this comparison (which Joe says uses data from Oct 7). The +/-5% discrepancy in magnitude at high frequency is around 600Hz, maybe it's a calibration line?
It might be worth making a plot like this for a stretch of time when the 508Hz noise was present in the C00 frames.